German Published Patent Application No. 195 37 619 describes a device for monitoring the road space of a motor vehicle, having at least one road-space sensor for detecting a body approaching the vehicle and a corresponding signaling system and/or a locking device for at least one door, which functions when the vehicle is standing still or almost standing still. The system or locking device is activated in response to a person/hand approaching at least one door handle, and, in response to the approach of a body in the road space, the opening of at least one door of the vehicle is prevented, rendered more difficult, or blocked, and/or an optical and/or acoustic signaling system indicates this approach of the body. In this context, at least one sensor detects the action state of the vehicle.
German Published Patent Application No. 100 56 569 describes a vehicle having at least one hinged door and a device for preventing the door from colliding with an object adjacent to the vehicle while the door is opened, a sensor having an evaluating logic circuit detecting the position and change of position of the object relative to the vehicle during a vehicle movement immediately preceding the opening of the door, and a warning signal or a locking device being triggered in response to the danger of a collision between the object and the vehicle door.
German Published Patent Application No. 198 36 310 describes a vehicle-door restraint device, which mechanically inhibits the opening of the door, at the latest, at or beyond an opening angle that is still safe, and/or which triggers an acoustic and/or optical restraint signal, the restraint device being controlled by a monitoring device, which monitors the exterior region of the vehicle for the presence of stationary and/or approaching obstacles, in particular in the opening region of the vehicle doors in question.
German Published Patent Application No. 198 08 181 describes a device for the collision protection of protruding parts of motor vehicles, the device having a controllable positioning mechanism for at least drawing in and/or folding in the protruding motor-vehicle parts. In this context, at least one distance sensor or proximity sensor, which is functionally connected to the positioning mechanism, is, e.g., situated in an outside mirror, and is for detecting the distance and/or the approach of an object relative to a specific, protruding motor-vehicle part, is provided on the vehicle, the positioning mechanism drawing in or folding in the motor-vehicle part in question in response to a detection signal that is supplied by the sensor and indicates a danger of colliding with the object. Sensors installed in the outside-mirror housings, and the detection results ascertained from their detection signals, may be used for further functions. Examples of this include a door-opening warning signal or the blocking of the opening of a door when an object is too close to the door to be opened.
German Published Patent Application No. 100 04 161 describes an adaptive door-handle lock for motor vehicles having a locking device, which enables or prevents the opening of a vehicle door as a function of at least one sensor-detected, vehicle-vicinity situation and includes a door-locking system, an environmental sensory system provided on or in the vehicle, and a monitoring device acting upon the door-locking system. The environmental sensory system generates signals that are supplied to the monitoring device, which control the door-locking system such that it keeps the door locked permanently, or for a certain or definable period of time, when the signals supplied by the environmental sensory system reveal that the safety in opening the door is questionable due to the vehicle-vicinity situation.
German Published Patent Application No. 41 19 579 describes a device for detecting objects not directly in the field of view of a motor vehicle, having a contactless distance-measuring device oriented in the field of view and a controlled door brake, which may be activated prior to or during the movement of the door, in response to an object approaching the vehicle.
Further safety systems for doors of a motor vehicle are described, for example, in PCT International Published Patent Application No. WO 96/33079 and Japanese Published Patent Application No. 3-61120.